Conventionally, in a lithography process to manufacture electronic devices (microdevices) such as a semiconductor device (such as an integrated circuit) or a liquid crystal display device, exposure apparatuses such as a projection exposure apparatus (a so-called stepper) of a step-and-repeat method or a projection exposure apparatus (so-called scanning stepper (also called a scanner)) of a step-and-scan method is mainly used.
This type of exposure apparatus is equipped with a substrate stage which moves on a stage base (hereinafter briefly shortened to a base, as appropriate), holding a substrate such as a wafer or a glass plate which serves as an exposure subject. As a driving source of this substrate stage, a substrate stage device is known which uses a planar motor including a mover that the substrate stage has and a stator that the stage base has (for example, refer to PTL 1).
In the planar motor used as the driving source of the substrate stage, there is an air flotation method in which the stage is levitated on the base by an air bearing and a magnetic levitation method according to PTL 1 described above in which the stage is levitated on the base by a magnetic levitation force generated by the planar motor. In the planar motor, there is a moving-magnet-type in which the mover includes a magnet and the stator includes a coil and a moving-coil-type in which the mover includes the coil and the stator includes the magnet. However, because it is not preferable for the stage to drag wiring and the like, in the substrate stage device, the moving-magnet-type planar motor is mainly employed.
Here, the case will be considered when the planar motor serving as the driving source of the substrate stage does not or cannot generate a driving force, such as when a breakdown of some kind occurs like the coil and/or a motherboard being damaged, or at the time of manufacturing or maintenance. In such a case, to move the substrate stage, in a substrate stage device that employs the planar motor of the magnetic levitation method, the substrate stage has to be lifted by human power, which is different from the planar motor of air flotation method where the levitated state of the substrate stage can be maintained by static pressure (so-called pressure in bearing clearance) of high-pressure air in between the bearing surface of the air bearing and the base upper surface. However, because the latest substrate stage weighs, for example, as much as 150 kg, the substrate stage cannot be lifted and moved alone by human power. If there is enough work space, while the substrate stage can be moved by several people working together, if there is not enough work space the substrate stage virtually cannot be moved. Therefore, as a method for overcoming this, while a proposal can be considered of providing wheels in a substrate stage via a vertical movement mechanism, in this case, the upper surface of the stator (base) has to be flat and also hard to some extent. However, because the stator upper surface of the moving-magnet-type planar motor that employs the magnetic levitation method is not so hard, microchannels on the stator side may be damaged by point load given via the wheels.